1. Field of the Invention
The present invention generally relates to the field of seismology, and more particularly to seismic sources, and most particularly to a piezoelectric borehole seismic source which may be emplaced into an active or inactive well in a permanent or semi-permanent manner.
2. Description of the Relevant Art
Currently, the standard way for addressing the need for producing borehole source waveforms is to lower a borehole source on a cable down an existing borehole. Due to the large diameters of the existing sources, concurrent well operation is impractical. Therefore, existing sources must be lowered, used, and then retracted. More importantly, for operating wells, production must be stopped, and production tubing retracted and removed before the desired tests can be conducted with the source in place. The source is then removed and production tubing replaced. This can be particularly expensive and time consuming when it is desired to take seismic readings at depths of several thousands of feet over extended periods of time. For pressurized wells, such as those used to inject or withdraw fluids and gases such as methane, oil, water or CO2, etc., pressure caps must additionally be used. As can be readily seen, such procedure is fraught with the possibility of borehole damage, and is extremely time consuming and labor intensive.
Accordingly what is needed in the oil and gas industry is a method of providing in-situ seismic source energy that may be generated as needed, concurrently with the operation and/or production of an existing well. Such continuous capabilities can be particularly useful in the monitoring of the condition of an oil field, or any other instance where fluids are injected or withdrawn from the ground using boreholes, such as when they are pumped down or have gases or fluids injected to facilitate oil extraction or any other fluid injection or withdrawal. The novel source described here is capable of performing such function, while not interfering with the continuous operation of the well, additionally allowing still other benefits such as pass through of needed gas and electrical lines from above to below the source.